Computers Mobile phones and other devices and equipment are often housed in metal housings or housings having at least some metal surfaces, which are generally protected by a surface coating. A surface finish which may be used on such devices or equipment is a metallic luster finish. However care is required to achieve a metallic luster appearance which shows the original metallic luster of the substrate surface and hides defects in the surface of the metal substrate when coating the surface using a painting process.